[ActionScript 3.0] AS3.0 火焰效果

package
{
    import flash.display.Sprite;
    import flash.display.*
    import flash.events.Event;
    import flash.filters.DisplacementMapFilter;
    import flash.geom.*
    /**
     * @author:Frost.Yen
     * @E-mail:871979853@qq.com
     * @create:    2016-6-28 下午3:37:51
     *
     */
    [SWF(width="1024",height="768")]
    public class FireEffect extends Sprite
    {
        private var bmd:BitmapData;
        private var target:Sprite = createSharp(400, 30,0);
        private var speed:Number = Math.random() * 4 + 4;
        private var strengh:Number = Math.random() * 60 + 60;
        private var size:Number = Math.random() * 17 + 20;
        private var randomseed:Number = Math.floor(Math.random() * 10);
        private var offset:Point = new Point();
        private var v:Point;
        private var w:Number = 50;
        public function FireEffect()
        {
            addChild(target);
            addTo(target);
            target.x = 0;
            target.y = 200;
        }
        private function createSharp(width:Number,height:Number,angle:Number):Sprite {
            var s:Sprite = new Sprite();
            s.graphics.beginFill(0, 0);
            s.graphics.drawRect( -w, -w, width + 2 * w,  w);
            s.graphics.beginFill(0xffffff);
            s.graphics.drawRect( -w, height, width + 2 * w,  w);
            var fillType:String = GradientType.LINEAR;
            var colors:Array = [0x900000, 0x900000,0xff9900,0xfffd8a,0xffffff];
            var alphas:Array = [0,1,1,1, 1];
            var ratios:Array = [0x00,0xff/16,0xff*2/6,0xff*2/3, 0xFF];
            var matr:Matrix = new Matrix();
            matr.createGradientBox(width, height, Math.PI / 2);
            var spreadMethod:String = SpreadMethod.PAD;
            s.graphics.beginGradientFill(fillType, colors, alphas, ratios, matr, spreadMethod);
            s.graphics.drawRect(0, 0, width, height);
            return s;
        }
        public function addTo(target:Object):void {
            bmd = new BitmapData(target.width, target.height);
            v = new Point(Math.random() * (speed / 4) - speed / 8,Math.random() * (speed / 4) + speed / 4 * 3);
            target.addEventListener(Event.ENTER_FRAME, update);
        }
        private function update(e:Event):void {
            target.filters = [new DisplacementMapFilter(bmd, new Point(), BitmapDataChannel.RED,BitmapDataChannel.RED, 10, strengh, "clamp")];
            offset=offset.add(v);
            bmd.perlinNoise(size / 2, size, 3, randomseed, false, true, 1, true, [offset, offset]);
        }
    }
}